Carburetor



E. OLSON Dec. 10, 1957 CARBURETOR origial Filed Aug. 9, 1949 JNVENToR. E/Im'er Olson 54 Af lorney m BY Hfs nited States Patent Ohice 2,815,942Patented Dec. 10, 1957 CARBURETOR Elmer lson, Rochester, N. Y., assignorto General Motors Corporation, Detroit, Mich., a corporation of DelawareOriginal application August 9, 1949, Serial No. 109,347, now Patent No.2,694,560, dated November 16, 1954. lgigiged and this application August3, 1954, Serial No.

2 Claims. (Cl. 261-52) This invention relates to carburetors forinternal combustion engines, particularly engines for automotive use,and is directed specifically to mechanism for operating the choke andthrottle valves of such carburetors.

It is the primary purpose of this invention to provide novel andimproved means for operating the choke and throttle valves of acarburetor which includes resilient means for manually moving anunbalanced choke valve to its closed position for cold weather starting,means for moving the throttle toward open position as the choke is movedto fully closed position in order to increase the idling speed for lowtemperature operation, and means for positively moving the choke valvetoward closed position from its fully open position in the event thatthe choke Valve gets stuck in the latter position.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Figure 1 is a view, partly in elevation and partly in vertical section,of a carburetor embodying the present invention; and

Figure 2 is a side elevation as seen from the left in Fig. 1.

The present invention is shown as embodied in a carburetor such asillustrated in copending application of Elmer Olson, S. N. 109,347,liled August 9, 1949, now Pat. No. 2,694,560, dated November 16, 1954,of which this application is a division. Since the invention to whichthis particular application is directed only to the mechansm foroperating the choke and throttle valves, the entire structure of thecarburetor is not shown and what is shown, other than the mechanismclaimed here in, is only briefly described.

The carburetor, which is of down-draft type, comprises three separatecastings 2, 4 and 6 positioned one above the other. The casting 2, whichcomprises the air inlet, is supported on top of the casting 4, in whichthe fuel chamber and the mixing chamber are positioned, and the casting4 is supported on the casting 6, in which the throttle valve whichcontrols the quantity of fuel mixture supplied to the engine isrotatably mounted. Suitable gaskets are positioned between the severalcastings. The air inlet passage is indicated at 8, and communicates withthe mixing chamber in casting 4 and the mixture formed therein isdelivered to the outlet passage 12 in casting 6.

Fuel is delivered to a constant level fuel chamber in the casting 4,through a Conduit 22 connecting with a passage 24 in casting 2. Apassage 26 in a nipple 28 connects passage 24 with chamber 20 and owthrough the passage 26 is controlled by a valve 30, which rests on arm32 operated by the usual float (not shown) in the conventional manner tomaintain a constant fuel level in chamber 20.

Fuel flows from the chamber 20 to main and idling fuel inlets through ametering plug 34 to a vertical passage 36 which connects at its upperend with a horizontal passage 38, formed in a tubular part of 'thecasting 2 which extends across the mixture passage. Fuel ows from thispassage through a restricted opening 40 into the main fuel supply nozzle42 which terminates in a small venturi tube 44, discharging into a largeventuri tube 46 formed by the wall of the mixing chamber.

The passage 38 extends all the way across the mixture passage and at itsleft end connects with the upper end of a vertical passage 48 in casting4, which leads to the idling fuel inlet (not shown). A plurality ofopenings Si) admit air to the passage 38 to form an emulsion of fuel andair therein.

The arrangement of fuel passages above describedl is the same as thatshown in the above-mentioned parentv application and since the specilicarrangement of such passages forms no part of the present invention, nomore detailed description of this structure is necessary herein.

Coming now to the mechanism which constitutes the present invention,admission of air through the air inlet 8 is controlled by an unbalancedchoke valve 52 secured oficenter to a shaft 54 journalled for rotationin the casting 2. Being rotatably mounted oit-center, the valve is, ofcourse, responsive to variations in suction within the carburetor and anincrease in such suction tends to open the valve. The throttle whichcontrols the quantity of fuel mixture supplied to the engine isdesignated at 56 and is secured to a shaft 58 journalled in the outletcasting 6.

The throttle is operated manually by an arm 60 secured to the flattenedend 62 of the shaft 58 and the usual operating connection extending tothe conventional accelerator pedal, and which is not shown, is adaptedto be connected to the swivel block 63 carried by the arm 66. When theunbalanced choke valve 52 moves toward open position, the shaft 54 movesclockwise, as seen in Fig. 2, and, of course, a reverse movement of theshaft is eiiected to move the choke valve toward closed position. Asalready indicated, the choke valve in the device disclosed is manuallyoperated, but instead of employing the conventional positive operatingconnection, the valve is moved to closed position through the medium ofa spring which may yield in response to the high suction created whenthe engine starts to run under its own power, to permit the valve toopen to some extent when this occurs.

The mechanism for operating the choke valve includes an arm 64 which isloose on the shaft 54 and this `arm is connected by a torsion spring 66which surrounds the shaft 54 with a second arm 68 fixed to the flattenedend 70 of shaft 54. One end of this spring is hooked vover the loweredge of arm 64 in a notch 72 and the other end of such spring is hookedover a rearwardly extending part of the arm 68 so that if arm 64 ismoved counter-clockwise, as seen in Fig. 2, the spring will pull downWardly on the arm 68 and will move the arm 68, the shaft 54 and valve 52counter-clockwise, to move said valve toward its closed position.Normally, the spring holds the arms 64 and 68 in the position shown inFig. 2, with the rearwardly extending portion of arm 68 in contact witha shoulder 74 on the arm 64.

The arm 64 carries a swivel block 76 and a Bowden cable (not shown), butextending to the instrument panel may be supported by a bracket 78secured to the carburetor housing, and connected to said swivel blockfor operating the arm 64.

A lever 8@ is pivotally mounted on a stud 82 which projects from thecasting 4 and is retained thereon by a washer 84 and screw 85, thislever being normally held in the position shown by the torsion returnspring which surrounds the stud and has one end 88 engaging the leverand the other end engaging a fixed lug 90 extending from the housing, asshown in Fig. 1. The arm 64 has a cam 92 formed thereon and this camserves to variably position the lever 80 as the arm is moved to controlthe position of the choke valve, such cam being engaged by `thelaterally extending upper end 94 of said lever, which is held inengagement with the cam by the spring 86.

The position of the lever 80 determines the idle position of thethrottle valve and for this purpose, the lever80, at its lower end, hasa laterally extending part 96 whichv is adapted to be engaged by a stopscrew 98, adjustable in an upwardly extending part 100 of the throttleloperating arm 60. Obviously, the position of the part96 will determinethe position of the throttle. If the part 96 is moved to the left, thethrottle will be opened and if moved to the right, the throttle will bemoved'to a more nearly closed position by its return spring.

.The cam 92 has a gradually increasing radius from the point a to thepoint b and beyond b terminates in a hump 102 of appreciable magnitude.If the arm 64 is moved counter-clockwise to effect closing of the chokevalve, the lever 80 will be rotated slightly clockwise so as togradually increase the opening of the throttle as the choke is movedtoward closed position and when moved to effect full closing of thechoke valve, as would beV desirable for starting in quite lowtemperatures, the

hump 102 becomes eiective and the opening of the throttle isconsiderably increased, so as to cause the engine to run much faster atidle than it does at normal operating temperatures.

The provision of the unbalanced choke and yielding operating means hasthe very practical advantage of eliminating the necessity of the drivermoving the choke valve toward open position immediately, when the enginebecomes self-operative, in order to prevent overchoking. The unbalancedvalve will open to some extent against the action of the spring, due tothe fact that the suction elective on such valve is suddenly and veryconsiderably increased when the engine begins to operate under its ownpower.

Sometimes, a choke valve will tend to stick in its wide open positionand a resilient operating connection such as disclosed, might have aspring which would not exert suicient force to release the valve. Inorder to eliminate -any difficulty arising from the possible sticking ofthe choke valve, a lug 104 is provided on the cam 92 and if the arm 64is moved counter-clockwise to a sufcient extent, such lug will engagethe rearwardly extending portion of arm 68, positively releasing thechoke valve and moving it toward closed position.

While the embodiment of the present invention as herein disclosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

, What is claimed is as follows:

1. In a carburetor having a mixture passage, a throttle controlling theow of combustible mixture through said 4' passage, a fuel supplychamber, means for supplying fuel to the mixture passage, an air inletadmitting air to said mixture passage, an unbalanced choke valvecontrolling the admission of air to said mixture passage and responsiveto variations in suction therein whereby an increase in suction in saidpassage tends to move said valve toward open position, a rotatable shafton which said choke valve is mounted, an operating arm secured tosaidshaft, a manually operable arm for moving the choke valve toward closedposition rotatable on said shaft, resilient means connecting said twoarms, said operating arm and resilient means being so related that thechoke valve may be rotated toward open position by suction with saidmanually operable arm in the fully closed choke position, a membermovable to diierent positions to determine the idling position of thethrottle valve, a cam having a contour of gradually increasing radiusintegral with said manually operable arm and engageable with said memberto move said member to elect gradual Vopeningof the throttle as said armis moved to effect closing of the choke valve, and a hump on the cam atone end of said contour adapted to engage said member when the manuallyoperable arm is moved to fully close said Choke valve to effecty anabrupt increase in the idle opening of the throttle when the choke isfully closed.

. 2. In a carburetor having a mixture passage, a throttle controllingthe ow of combustible mixture through said passage,` a fuel supplychamber, means for supplying fuel to the mixture passage, an air inletadmitting air to said mixture passage, au unbalanced choke valvecontrolling the admission of air to said mixture passage and responsiveto variations in suction therein whereby an increase in suction in saidpassage tends to move said valve toward open position, a rotatable shafton which said choke valve is mounted, an operating arm secured to saidshaft, a manually operable arm for moving the choke valve toward closedposition rotatable on said shaft, resilient means connecting said twoarms, a throttle, a lever fixed for rotation with said throttle, a leverpivotally mounted intermediate its ends on said carburetor, a camintegral with said manually operable arm and engageable with one end ofsaid pivoted lever, an adjustable stop element mounted on said throttlelever and adaptedto abuttingly engage the other end of said pivotedlever to determine the idle position of the throttle in accordance withthe position of said cam, and additional `resilient means coactinglydisposed intermediate said carburetor and the pivoted lever tocontinuously urge the said one end of the pivoted lever into engagementwith said cam.

References Cited in the le of this patent UNITED STATES PATENTS2,003,403 Timian June 4, 1935 2,140,776 Trisler Dec. 20, 1938 2,124,777Hunt et al. July 26, 1938 2,478,613 Weber Aug. 9, 1949

